In vertebrates, rhodopsin is the main intrinsic membrane protein component of the retinal rod outer segment's discs. In the process of vision, the primary event in the transduction of light energy into a nerve impulse is the absorption of light by rhodopsin. Shortly after this absorption of light, the plasma membrane of the rod cell lowers its permeability to Na ion and a change in membrane potential occurs which initiates the successive conduction/transmission processes of the visual neuronal pathways. The main objective of the proposed work is to understand better what molecular mechanisms mediate the transduction of light absorption at the disc membrane into the change in membrane potential at the rod outer segment membrane. In particular, we intend to test the hypothesis that rhodospin might behave as a light activated passive-permeability pathway for intra-disc Ca ions to be released into the rod outer segment cytoplasm which subsequently modulates the plasma membrane's Na ion permeability. We propose to incorporate rhodospin into artificial lipid bilayer membranes and measure any light-induced, ion-specific, charges in the reconstituted membrane's permeabiligy by coupled electro-optical techniques.